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Hurricane Ernesto Discussion Number  29
NWS National Hurricane Center Miami FL       AL052024
500 PM AST Sun Aug 18 2024

The structure of Ernesto this afternoon has continued to improve, 
with a more distinct eye becoming apparent on recent visible and 
infrared satellite images. This improving inner-core structure is 
also exhibited in a 1808 UTC GMI microwave pass that also showed a 
closed cyan ring on the 37-GHz color composite channel, which could 
be a harbinger for more significant intensification. While 
subjective Dvorak estimates have not increased much this afternoon, 
the objective intensity values now range from 60-69 kt and so the 
initial intensity was raised to 65 kt, making Ernesto a hurricane 
again. Ernesto's wind field is a bit smaller than yesterday, as 
indicated by a helpful set of scatterometer passes over Ernesto that 
were useful to adjust the 34- and 50-kt wind radii earlier today.

With the improving inner-core structure, Ernesto is looking 
increasingly likely to take advantage of the favorable short-term 
conditions until the hurricane reaches the northern extent of the 
Gulf Stream at around 40 N. The raw output form the 
hurricane-regional model guidance now all show an overnight or 
Monday morning peak intensity of 75-kt or higher in the next 12-24 
h, and the latest NHC intensity forecast now shows a bit more 
intensification overnight. However, Ernesto will quickly move over 
cooler ocean waters just after 12 h and weakening will likely be 
well underway by tomorrow afternoon. Shear is also forecast to 
increase after that time as well, and my best guess at the timing of 
extratropical transition, diagnosed by FSU cyclone-phase space 
diagrams and GFS/EC simulated satellite imagery, is shortly after 
36 h on Tuesday morning as Ernesto passes just southeast of 
Newfoundland. The NHC intensity forecast is on the upper-end of the 
interpolated guidance aids in 12 h, but falls back to the 
multi-model intensity mean towards the end of its lifespan in 60-h 
where the cyclone will open up into a trough over the central North 
Atlantic. 

Ernesto continues its gradual acceleration north-northeast, 
estimated now at 020/15-kt. A further increase in forward motion 
with a turn more northeastward is anticipated over the next 24-36 h 
as Ernesto becomes caught up in the flow between a large deep-layer 
trough over the eastern U.S. and a subtropical ridge centered to the 
hurricane's southeast. A turn more east-northeastward is expected 
thereafter before the cyclone becomes absorbed by a larger 
extratropical cyclone located further north between Greenland and 
Iceland. The track guidance this cycle remains tightly clustered 
and pretty close to the prior forecast track, and only slight track 
adjustments were made this cycle. On this track, Ernesto should 
make its closest approach to Newfoundland just to the southeast 
early Tuesday morning, with the bulk of the cyclone's wind field 
staying offshore of the Canadian Provence.
 
Key Messages:
 
1. Even though Ernesto is forecast to remain well offshore of the 
U.S. East Coast, swells generated by the hurricane will continue to 
affect the area through the early part of this week.  Beach goers 
should be aware that there is a significant risk of life-threatening 
surf and rip currents, and should stay out of the water if advised 
by lifeguards.  Surf and rip currents are also possible on the 
Bahamas, Bermuda, and Atlantic Canada during the next few days.
 
2. Ernesto could bring wind, wave, and rain impacts to portions of
southeastern Newfoundland Monday night into Tuesday morning.
Breaking waves could bring the possibility of coastal flooding,
particularly along southwest-facing shorelines from Bunin east to
Avalon regions. For additional impact specific information, please
see statements issued by the Canadian Hurricane Centre.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  18/2100Z 37.1N  62.3W   65 KT  75 MPH
 12H  19/0600Z 39.2N  60.9W   75 KT  85 MPH
 24H  19/1800Z 42.6N  57.1W   70 KT  80 MPH
 36H  20/0600Z 46.1N  50.7W   55 KT  65 MPH
 48H  20/1800Z 48.9N  41.3W   45 KT  50 MPH...POST-TROP/EXTRATROP
 60H  21/0600Z 51.0N  29.5W   40 KT  45 MPH...POST-TROP/EXTRATROP
 72H  21/1800Z...DISSIPATED
 
$$
Forecaster Papin
 
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